remove workaround for old versions of process

ghc 8.4.4 has process 1.6.3, which was the first version to include
getPid.

Remote/Helper/Ssh.hs

@@ -29,7 +29,6 @@ import qualified P2P.Annex as P2P
 import Control.Concurrent.STM
 import Control.Concurrent.Async
 import qualified Data.ByteString as B
-import Data.Unique
 
 toRepo :: ConsumeStdin -> Git.Repo -> RemoteGitConfig -> SshCommand -> Annex (FilePath, [CommandParam])
 toRepo cs r gc remotecmd = do
@@ -262,16 +261,14 @@ openP2PSshConnection r connpool = do
 				, std_out = CreatePipe
 				, std_err = CreatePipe
 				}
-		-- Could use getPid, but need to build with older versions
-		-- of process, so instead a unique connection number.
-		connnum <- hashUnique <$> newUnique
+		pidnum <- getPid pid
 		let conn = P2P.P2PConnection
 			{ P2P.connRepo = repo
 			, P2P.connCheckAuth = const False
 			, P2P.connIhdl = to
 			, P2P.connOhdl = from
 			, P2P.connIdent = P2P.ConnIdent $
-				Just $ "ssh connection " ++ show connnum
+				Just $ "ssh connection " ++ show pidnum
 			}
 		stderrhandlerst <- newStderrHandler err
 		runst <- P2P.mkRunState P2P.Client